Interpretive Summary: Freezing and thawing semen results in compromised sperm function and in vitro fertilization (IVF) success. Semen samples are often evaluated to determine the motility prior to use for in vitro fertilization and samples that fall below a designated motility threshold are often not used. Our objective was to determine if post-thaw sperm motility, sperm quality characteristics, or a novel assay of sperm oviduct binding were related to IVF success. Our results indicate that post-thaw motility of frozen-thawed boar sperm is strongly related to acrosome membrane integrity but has limited use for predicting IVF success. The number of sperm bound to oviduct cells was related to IVF polyspermy rates and may be more indicative of in vitro sperm function than traditional sperm motility and physiology characteristics.

Technical Abstract:
Cryopreserved semen allows the use of single ejaculates for repeated analyses, potentially improving in vitro fertilization (IVF) consistency by eliminating inter-ejaculate variability observed with fresh semen. However, the freezing and thawing processes result in compromised sperm function and IVF success. Semen samples are often screened for motility prior to use for IVF. Samples that fall below a designated motility threshold may be discarded. Our objectives were to determine if post-thaw sperm motility, other traits that may be indicative of sperm function or a novel assay of oviduct binding were related to IVF success. Semen from 16 boars was cooled to 15°C for overnight shipment prior to cryopreservation. Semen was thawed and motility was recorded microscopically and confirmed using Computer Automated Sperm Assessment (CASA). Each sample was tested by IVF in two to three independent replicates. Regression and correlation analyses were employed to determine the interrelationships between sperm traits and the relationships between post-thaw motility, sperm-oviduct binding and IVF outcomes. Among sperm traits examined, sperm acrosome integrity was negatively correlated with post-thaw motility (r2 = 0.64) but not with IVF results. The number of sperm bound to oviduct aggregates was correlated with IVF polyspermy rates (r2 = 0.62, P < 0.05) but less with overall IVF fertilization rates (r2 = 0.31, P > 0.10). There was some relationship of post-thaw motility with IVF monospermic fertilization (P = 0.06, r2 = 0.08) but not to other IVF outcomes. Our results indicate that post-thaw motility of frozen-thawed boar sperm is strongly related to acrosome integrity but has limited use for predicting IVF success. The number of sperm bound to oviduct cells was related to IVF polyspermy rates and may be more indicative of in vitro sperm function than traditional sperm motility and acrosome status evaluation.